The invention relates to a vehicle seat having parts for carrying out a vibratory motion in the height direction, which parts comprise a base part, a top part and a height adjustable connection frame arranged there between, as well as at least one spring element, according to the preamble of Patent Claim 1.
It is customary within the vehicle sector that two vehicle parts which are capable of a vibratory motion relative to each other comprise, such as e.g. a seat part having a top part of a vehicle seat, which is spring mounted relative to a vehicle base part, a spring element as well as an additional damping element in the form of a damper, in order to take energy out of the suspension system and to dampen the spring movement, if large deflections of this springy vibrating system are caused in a case of resonance.
Such dampers may be designed in different ways. For example, hydraulic dampers essentially consist of a piston rod having a piston guided in an oil-filled cylinder. During an axial movement of the piston rod with and as a result of the piston relative to the cylinder, the oil has to flow through narrow channels and valves in the piston. As a result of the resistance acting against the oil in the course of this, pressure differentials are generated which generate the damping forces across active surfaces. As the speed of the piston movement increases, the flow resistance and thus the damping action increases, and this characteristic may be specifically influenced within certain limits.
Also known are mechanical shock absorbers which in principle consist of spring-loaded frictional surfaces. The coated leaf springs have several spring elements and represent combined spring/damper units. The shock is absorbed by the flexion of the spring and is stored in the spring. The friction between the individual spring leaves dampens the vibration and converts part of the spring forces into heat.
Also known are air spring dampers wherein the medium air, can carry out both spring and damping actions.
Frequently, such an arrangement of a damper, for example in a vehicle seat or between a driver cabin and a vehicle chassis, requires a complex design in order to obtain an optimum damping of vibrations orientated in different directions and being of different intensities. It is necessary to consider an accurate coordination between the damping and the spring properties, which are to enable for example a seat comfort area within a characteristic curve of spring deflection against force of a vibrating vehicle seat. Moreover, these damper systems have the disadvantage of reducing vibration reduction in the hypo- and hypercritical ranges and thus lead to a deterioration of vibration comfort.